Sulfuric acid is an important catalyst widely used for various chemical reactions. However, sulfuric acid has a number of problems, for example, that sulfuric acid is generally required in large amounts, has a problem of apparatus corrosion and requires steps for separating, collecting from the product after the reaction, step for purifying and reusing the collected sulfuric acid, and requires, steps for neutralizing sulfuric acid remained in the product and removing salt generated thereby, and steps of disposal, waste water treatment and the like, and further, these steps require a lot of energy, and the like.
By using a solid acid catalyst as a substitute for mineral acid catalyst such as sulfuric acid, solid acid catalyst is useful as a catalyst for various chemical reactions since the various steps after the above reactions can be omitted or substantially simplified without apparatus corrosion, and various types of solid acids have been developed. Typical solid acids are inorganic compounds such as silica-alumina, crystalline aluminosilicate (zeolite), and heteropoly acid.
On the other hand, the hydration reaction of olefins is an industrially important reaction for the production of alcohols and ketones, and an acid catalyst is used for the reaction. Isopropyl alcohol or 2-butanol is produced by various methods using hydration of propylene or n-butene (Non-Patent Document 1 and Non-Patent Document 2). In many processes of hydration reaction step, sulfuric acid is used as a catalyst. However, in addition to the above-mentioned problems, sulfuric acid has a problem that it generates many by-products, so that solid acid catalysts are also partially used for the purpose of resolving these problems. In this case, the above-mentioned inorganic solid acid catalysts are not used since their activities are generally lowered in the presence of water, and catalysts comprising phosphoric acid supported on an inorganic carrier and the like are used. However, there is a problem that the phosphoric acid is detached from the carrier during the reaction. In addition, a strong acid type of ion-exchange resin, a polymer having a sulfonic acid group on the skeleton of a cross-linked polystyrene, is also used, but its range of use is limited due to problems such as having low heat resistance and expensiveness of the resin. A fluorine-substituted olefin polymer-based solid super strong acid “NAFION” (a registered trademark of DuPont) having heat resistance or the like has been also developed, but it is too expensive to be used for industrial purposes.
In such a situation, a sulfonic acid group-containing carbonaceous material obtained by carbonization and sulfonation of an organic matter such as an aromatic compound or saccharide at a relatively low temperature has been developed, and the material is recently attracting attentions due to high activities for various chemical reactions as a catalyst, excellent heat resistance, inexpensiveness and the like, and the evaluation thereof is being tried as a catalyst for esterification reaction of a fatty acid, hydrolysis reaction of an ester, alkylation reaction and hydration reaction of an olefin, or the like (Non-Patent Document 3, Non-Patent Document 4, Non-Patent Document 5, Patent Document 1, and Patent Document 2). However, for example, with respect to the hydration reaction of an olefin, only an example in which 2,3-dimethyl-2-butene is hydrated to give 2,3-dimethyl-2-butanol in low yield is reported, and the development of a solid acid catalyst with further higher activity has been desired from the viewpoint of practical use. Incidentally, it is well known that normal butene is hydrated to give 2-butanol, and 2-butanol is dehydrogenated to give methyl ethyl ketone. Methyl ethyl ketone is one of the very important industrial chemicals as solvents for paint, ink, adhesive and the like, and cleaning agents for various purposes. 2-butanol is currently produced by a method using sulfuric acid as a catalyst, a method using a heteropoly acid catalyst, or the like. However, the sulfuric acid method has problems of waste sulfuric acid and apparatus corrosion, while the heteropoly acid method involves advanced technology such as using a supercritical state. Therefore, an inexpensive and effective technology for producing 2-butanol has been desired.
In addition, a method for decomposing cumene hydroperoxide to produce acetone and phenol is an industrially very important chemical process. This reaction progresses under acid catalyst, and dilute sulfuric acid is currently used (Non-Patent Document 7). Sulfuric acid aqueous solution is highly corrosive and has a problem of waste sulfuric acid. In addition, sulfuric acid aqueous solution has problems in which a large amount of energy is required to separate the product from the reaction solution, and the like. Therefore, an alternative solid acid catalyst has been desired.
Furthermore, Patent Document 2 and Patent Document 3 disclose proton (ion) conductor materials comprising a sulfonic acid group-containing carbonaceous material obtained by carbonization and sulfonation of various organic matters and also disclose an application to battery as a solid electrolyte. However, the conductivity of these proton conductor materials is still not sufficient and emergence of a material showing further excellent conductivity is anticipated.
On the other hand, it is known since long time that a specific organic matter is heated at high temperature, whereby a carbonized materials with high specific surface area (so-called, activated carbon) is obtained, and a carbonized materials obtained by using phenolic resin as a raw material is also disclosed (for example, Non-Patent Document 6 and Patent Document 4). The carbonized materials disclosed in these documents are obtained by subjecting a phenolic resin to heat treatment at a very high temperature over 700° C. Even though these carbonized materials are sulfonated, many sulfonic acid groups are not introduced, and high catalytic activities for various chemical reactions and the proton conductivity cannot be provided. In this regard, these carbonized materials are much different from the above-described sulfonated carbonaceous materials.    [Non-Patent Document 1] Shokubai, 18(6), 180 (1976)    [Non-Patent Document 2] Sekiyu Gakkaishi, 34(3), 201 (1991)    [Non-Patent Document 3] Domen et al., “Synthesis conditions and catalysis of carbon-based strong solid acids,” 85th Annual Meeting (Spring) of the Chemical Society of Japan (2005), 2B5-43    [Non-Patent Document 4] Hara, M. et al. Nature, 438(10), 178, November (2005)    [Non-Patent Document 5] Hara et al., PETROTECH, 29(6), 411 (2006)    [Non-Patent Document 6] Enda et al., “Carbonization and Activation Behaviors of Waste Phenol Resin,” Proceedings of the 16th Annual Conference of the Japan Society of Waste Management Experts (2005), 758, C1-8    [Non-Patent Document 7] Shin Sekiyu Kagaku Process, p 239 (1986), SAIWAISHOBO    [Patent Document 1] Japanese Patent Laid-Open No. 2004-238311    [Patent Document 2] International Patent Publication No. WO2005/029508 A1    [Patent Document 3] Japanese Patent Laid-Open No. Hei 3-167712    [Patent Document 4] Japanese Patent Laid-Open No. Hei 5-43348